Every spring in April, we hear on the news that the Tateyama-Kurobe Alpine Route has been cleared of snow to create these snow walls on the mountain road (upper left photo). Another major harbinger of spring when tour buses pass through these snow walls.
The Tateyama-Kurobe Alpine Route is one of Japan’s most enjoyable and scenic tour routes especially in April–May before the snow walls (15 to 20 meters high) melt. The tour route is 37 km long through the Tateyama Mountains and takes most of the day to go through.
Great fun since you ride so many different things: Cable car, bus, trolley bus, and ropeway. And the scenery keeps changing dramatically. Snow walls, snowy mountains, alpine lake, and you also walk across Kurobe Dam (upper right photo).
The lower left photo shows the Tateyama Mountains and ropeway down to Lake Kurobe and Kurobe Dam. It was taken from a scenic point called Daikanbo (大観峰). To board the ropeway, you pass through a small snow tunnel (lower right photo). There’s also time for walking around in the snow to get high on the fresh mountain air. If you’re super lucky and have sharp eyes, you might see the snow grouse (raicho 雷鳥).
I started the tour from Tateyama Station and went all the way to the end to Shinano-Omachi Station in Nagano Prefecture. You can also go in the opposite direction. Most of the route is in Toyama Prefecture. The tour is kind of pricey, costing around ¥13,000 to ¥14,000 one way for adults. The route is open from mid-April to late Nov.
If you have an extra day or two, there are great side trips on both ends of the route. In Toyama, the Kurobe Gorge Train Tour (黒部峡谷とトロッコ) from Unazuki Station is very scenic. And from Shinano-Omachi Station in Nagano, take a train to Matsumoto to see Matsumoto Castle (National Treasure) and other sights. 
Official: https://www.alpen-route.com/en/